1. Field of the Invention
This invention relates generally to Voice Over Internet (VoIP) protocols and architectures. More particularly, it relates to location based services for the provision of 911 emergency services using VoIP protocols and architectures.
2. Background of the Related Art
911 is a phone number widely recognized in North America as an emergency phone number that is used by emergency dispatch personnel, among other things, to determine a location of a caller. Enhanced 911 (E911) is defined by the transmission of callback number and location information. E911 may be implemented for landline and/or wireless devices.
A Public Safety Answering Point (PSAP) is a dispatch office that receives 9-1-1 calls from the public. A PSAP may be a local, fire or police department, an ambulance service or a regional office covering all services. A 9-1-1 (“911”) service becomes E-9-1-1 (“E911”) when automatic number identification and automatic location information from a communications device (e.g. wireless phone, VoIP Phone, etc.) is provided to the 911 operator.
Voice-Over-Internet Protocol (VoIP) is a technology that emulates a phone call, but instead of using a circuit based system such as the telephone network, utilizes packetized data transmission techniques most notably implemented in the Internet. 911 calls made using VoIP technology must reach the correct PSAP, but there currently is no uniform interface to the various PSAPs for call delivery because the technology for connecting calls varies. For instance, not all PSAPs are Internet Protocol (IP) capable. Some PSAPs are accessed via ordinary public switched telephone network (PSTN) telephone lines. Some PSAPs are accessed through selective routing such as direct trunks. Still other PSAPs are accessed using IP connections. There is no uniformity among the thousands of different PSAPs.
Moreover, some Public Safety Access Points (PSAPS) are not enhanced, and thus do not receive the callback or location information at all from any phone, landline or wireless.
The use of VoIP technology is growing quickly. As people adopt voice-over-IP (VoIP) technology for routine communications, the inventors herein recognize that there is a growing need to access E911 services including provision of location information from a VoIP device.
The existing E911 infrastructure is built upon copper wire line voice technology and is not fully compatible with VoIP. Given VoIP technology, there are at least three VoIP scenarios:                1. A VoIP UA that is physically connected to a static data cable at a “home” address. For instance, an Analog Telephone Adapter (ATA) that is connected to the “home” data cable and uses traditional telephone devices.        2. A VoIP UA that is physically connected to a data cable at a location different than its “home” address. For instance, a laptop computer device utilized away from home as a VoIP software telephone would be a VoIP ‘visitor’ device as described by this scenario.        3. A VoIP UA that is wireless, physically disconnected from any data cable. In this situation, the VoIP UA connects to the VoIP service provider via either a wide-are wireless technology (e.g., cellular, PCS, WiMAX) or via a local-area wireless technology (e.g., Wireless Fidelity (WiFi), UWB, etc.) using a laptop computer or handheld device.        
VoIP phone calls are routed to a VoIP voice gateway, from which they are passed on to their destination. A VoIP voice gateway or soft switch is a programmable network switch that can process the signaling for all types of packet protocols. Also known as a ‘media gateway controller,’ ‘call agent,’ or ‘call server,’ such devices are used by carriers that support converged communications services by integrating SS7 telephone signaling with packet networks. Softswitches can support, e.g., IP, DSL, ATM and frame relay.
The challenges evident with respect to determining the location of a calling VoIP telephone is perhaps most evident with respect to its use to make an emergency call (e.g., a 911 call). Nevertheless, VoIP telephone technology is quickly replacing conventional switched telephone technology. However, because VoIP is Internet Protocol (IP) based, call related information such as CallerID type services may not be available or accurate. A location of a given VoIP device may be provisioned to be at a given geographic location, or queried from a home location register (HLR) in a mobile system.
In addition, some Public Safety Access Points (PSAPs) are not enhanced, and thus do not receive the callback or location information at all from any phone; landline, cellular or VoIP.
Moreover, there is complexity in public access to Public Safety Answering Points due to lack of a Session Initiation Protocol (SIP) Uniform Resource Identifier (URI) for all PSAPs. (SIP is the IP-based protocol defined in IETF RFCs 3261 and 2543.) SIP is one of two dominant protocols used by the VoIP industry. URI is the addressing technology for identifying resources on the Internet or a private intranet. URIs were originally defined as two types: Uniform Resource Locators (URLs) which are addresses with network location, and Uniform Resource Names (URNs) which are persistent names that are address independent. Today, a URI is defined by its purpose rather than the URL vs. URN classification.) Some PSAPs are accessed only by conventional telephone line, others only by direct telephone trunk lines. Not all PSAPs are accessible via the Internet.
FIG. 6 shows basic conventional VoIP elements required to interconnect a VoIP emergency E911 caller to a relevant public safety access point (PSAP).
In particular, as shown in FIG. 6, VoIP telephone devices 102a, 102b, 102c (collectively referred to as 102) are connected to respective VoIP Service Provider (VSP) soft switches 104a, 104b, 104c (collectively referred to as 104) using an Internet Protocol (IP) connection, most commonly over the Internet. The VoIP service provider's soft switch 104 in turn communicates with a respective VoIP Positioning Center (VPC) 106a, 106b, 106c (collectively referred to as 106) using an appropriate IP connection. Each VSP requires use of their own VPC, as depicted in FIG. 6.
FIG. 7 shows in more detail conventional VoIP elements required by a VPC to interconnect a VoIP emergency E911 caller to a relevant public safety access point (PSAP).
In particular, as shown in FIG. 7, each VPC 106 comprises its own respective route determination module 404, call delivery module 406, and provisioning list 408.
A respective location information server (LIS) 108 services each of the VPCs 106. The LIS 108 is responsible for storing and providing access to the subscriber location information needed for E9-1-1 call processing (as defined by the NENA VoIP Location Working Group).
A conventional VoIP Positioning Center (VPC) 106 is a system that attempts to determine the appropriate or correct PSAP 114 that a VoIP emergency E911 call should be routed to based on the VoIP subscriber's position. The conventional VPC 106 also returns associated routing instructions to the VoIP network. The conventional VPC 106 additionally provides the caller's location and the callback number to the relevant PSAP through the automatic location identifier (ALI) (The ALI is a database that accepts a PSAP query, and using that relates a specific telephone number to a street address. In the case of an Emergency Services Query Key (ESQK), the ALI database steers the query to the appropriate VPC and steers the response back to the PSAP. An ALI is typically owned by a LEC or a PSAP.)
Further as shown in FIG. 7, each VSP route the emergency 9-1-1 call, without location object added, to their VPC 106. The VPC must determine the correct PSAP 114 (collectively represented by PSAP 114a, 114b and 114c) and route to it using the appropriate technology.
In a first scenario, the VPC 106 passes the 9-1-1 call to the PSAP 114a using an INVITE telephone number message, via a media gateway 110 that translates between the IP protocol of the INVITE message and a telephone line interface, and interfaces with the public switched telephone network (PSTN) 112.
In a second scenario, the VPC 106 passes the 9-1-1 call to the PSAP 114b using an INVITE S/R message, via an ESGW 120 and selective router 122. In this scenario, the selective router 122 is connected to the relevant PSAP 114b via direct trunks.
In a third scenario, the VPC 106 passes the 9-1-1 call to the PSAP 114c using an INVITE PSAP message, via IP, to the PSAP 114c. 
In the second and third scenario, the ALI 126 must be inter-connected with each VPC 106 (a,b,c). Furthermore, each VPC is burdened with supporting all the various ALI protocols: ve2, e2, PAM, legacy NENA, etc.
Thus, as can be appreciated, an Emergency call (e.g., 911, E911) may require the involvement of one or more Response Centers (RCs), e.g., Public Safety Access Point (PSAP) in addition to the RC that initially receives the emergency call. This is because there is a possibility that the emergency call is received by a PSAP other than that which is assigned to the geographic region that the caller is currently located in.
Accordingly, the PSAP that initially answers the call may need to transfer the emergency call to the correct PSAP. During transfer of the emergency VoIP call, the original RC may or may not remain on the line, but for safety purposes will not likely want to disconnect or cold transfer the emergency call. This is because errors may occur in the transfer, resulting in valuable time lost. One cause of a faulty transfer of the E911 call would be that the VoIP user has not updated the location stored by the VPC, or quite simply that bad routing has occurred. Another cause would be that the nature of the emergency requires multiple parties to be involved (e.g., fire/police, police/FBI, ambulance/CDC, etc.).
Conventional solutions are based on tools that can be used to find the phone numbers of other emergency response centers. The ERC receiving the call initially will perform a look-up for the correct response center, and may dial the identified correct response center, agency, etc., and transfer the call via direct dial/public switched telephone network (PSTN.
One exemplary conventional solution is called an Intelligent Emergency Network (IEN), available from Intrado Inc. of Longmont, Colo. However, such conventional solutions typically require the emergency response center to know the direct dial lines of every PSAP, ESP, ERC, etc. nationally. Moreover, those lines may not always be staffed. Other potential problems would be caused if no automatic location identification (ALI) information is accessible or available.
There is a need for an architecture and methodology that both simplifies the complexity of a VoIP call transfers with respect to an emergency response center such as a public safety access point (PSAP).